Revert "Pipeline operators: && and ||" (#7452)

Reverts nushell/nushell#7448

Some surprising behavior in how we do this. For example:

```
〉if (true || false) { print "yes!" } else { print "no!" }
no!
〉if (true or false) { print "yes!" } else { print "no!" }
yes!
```

This means for folks who are using the old `||`, they possibly get the
wrong answer once they upgrade. I don't think we can ship with that as
it will catch too many people by surprise and just make it easier to
write buggy code.

crates/nu-parser/src/flatten.rs

@@ -455,10 +455,14 @@ pub fn flatten_pipeline_element(
             output.append(&mut flatten_expression(working_set, expr));
             output
         }
-        PipelineElement::Or(span, expr) => {
-            let mut output = vec![];
+        PipelineElement::And(span, expr) => {
+            let mut output = vec![(*span, FlatShape::And)];
+            output.append(&mut flatten_expression(working_set, expr));
+            output
+        }
+        PipelineElement::Or(span, expr) => {
+            let mut output = vec![(*span, FlatShape::Or)];
             output.append(&mut flatten_expression(working_set, expr));
-            output.push((*span, FlatShape::Or));
             output
         }
     }